I want to view large images that I transfer to my iPhone from my computer. Obviously I cannot view them completely at a 1:1 ratio, but rather I want to be able to zoom in to the 1:1 ratio. The only application that I have found is Full-Res, which claims to do what I am looking for, but falls far short of giving you a full size image.

If it helps, I specifically want to view JPG and PNG images that are between 5,000x5,000 and 10,000x10,000 at 72dpi. I have no problem opening them up in the default Photos application, but using the "pinch and zoom" technique does not zoom very far at all.

Viewing maps is off-topic, and probably best on apple.stackexchange.com. But, this image resolution isn't at all unreasonable for full photographs; the Canon T3i generates 5184×3456 files, and 7264×5440 for the Pentax 645D. So this seems reasonably on-topic here — we entertain questions about software for photo presentation on other platforms without blinking an eye.
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mattdmJun 3 '11 at 3:23

I have modified my question to ask about images. They are, the same thing from this perspective after all :-) I specifically asked my question about "images" and only added the "maps" part as a secondary note if it was necessary to assist in answering the question. Forgive me.
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dpollittJun 3 '11 at 3:25

Feel free to downvote, just comment on what you are downvoting for please.
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dpollittJun 3 '11 at 13:44

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Can care to comment what it means "falls far short of giving you a full size image"? According to the reviews on the app store some people are using it fine.
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Grzegorz Adam HankiewiczJun 3 '11 at 19:44

2 Answers
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Reputedly, the Image Viewer app will allow you to "zoom image at actrul size" (sic.). It might be worth checking out if you can get past the Engrish.

However, the major problem may be that if you use iTunes to transfer your photos onto the iOS device it will "optimise" or downscale your photos during the sync. Finding other ways of transferring files such as using Dropbox may circumvent this shortcoming.

Well, I do use iTunes to transfer the images. I didn't know it did any downsizing of the images. Do you have a source of that info?
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dpollittJun 14 '11 at 16:20

That came as a surprise to me too but I tested it and fmark is correct. A 5616x3744px 5.04MB image transferred to my iPhone via iTunes then brought back either via Dropbox (at full size) or e-mail (full-size) has become 2304x1536px 1.22MB. A 1040x1536px 600KB wallpaper image transferred the same way is still the same dimensions but now 403KB. So it looks like (on an iPhone 5 running iOS 7) iTunes shrinks to a max size of 1536px and applies compression.
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Mark WhitakerOct 3 '13 at 20:18

As you noticed, photo transfers using itunes or iPhoto will downscale the images, which is why pinch to zoom will not zoom in very far.

I am the developer of an iPhone app that does allow you to view images in their native resolution. There is unfortunately a hoop to jump through which is that images have to be converted on a computer into a format that preserve the native resolution yet is easy to display on the iPhone / iPod touch. You can then transfer that file to the app on the iPhone using the iTunes file transfer or the built in sharing service of the desktop and iPhone app.

The converter is a free and open source Java app and the iPhone app is paid but universal.

You can zoom into the images at 100% on non-retina devices, and 200% on retina devices. I tested it to work with images up to 21000 x 21000 pixels.

Thanks for following the disclosure rules. This makes me even more glad I don't have an iPhone, but I'm glad you've put in the effort to produce a clever work around for those who do. Hope it works out well for you, certainly sounds like a good way around the problem.
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AJ HendersonOct 3 '13 at 14:31